The present invention relates to a liquid crystal module, and more particularly to a liquid crystal module having a liquid crystal panel with a sidelight-type backlight disposed on the rear surface thereof.
In the case of a liquid crystal module that provides a display using light coming from the outside, the backlight is generally located on the rear surface of the liquid crystal panel. In addition, modules using a linear light source (such as a cold cathode fluorescent tube) as a backlight are well-known. The backlight, acting as the linear light source, basically comprises two types, depending on the arrangement method of the linear light source. One type is the so-called direct-type backlight where the linear light source is placed directly under the liquid crystal panel. This type of backlight is mainly employed for a liquid crystal TV set using a large-sized liquid crystal panel requiring high brightness.
The other type of backlight is the so-called sidelight-type backlight where the linear light source is positioned on the side of the light guiding plate that is arranged directly under the liquid crystal panel. The sidelight-type backlight is often employed for the monitor of a personal computer which requires a low-profile, or an in-vehicle monitor, and the like.
One example of the configuration of the sidelight-type backlight is described in Japanese Patent Laid-Open Publication No. 11-258601 (JP, 11-258601, A1), where the light guiding plate (also referred to as the light guide) is located on the rear surface of the liquid crystal panel, and an optical sheet (such as a diffusion plate) is arranged between the liquid crystal panel and the light guide, and a reflector resides on the rear surface of the light guide. In such manner, a lamp serving as the linear light source is arranged on the side of the light guide.
Usually, so-called lamp holders, made of an elastic member such as silicon rubber, are attached on both ends of the linear light source to support it.
The configuration of the structure around the lamp holders supporting the linear light source will hereafter be described in more detail with reference to the cross-sectional view of FIG. 6, which shows an example of the sidelight-type backlight liquid crystal module of the prior art.
Reference numeral 10 represents a liquid crystal panel comprising a pair of transparent substrates, a liquid crystal layer (not shown) formed between the pair of transparent substrates, and polarizers that are adhered to the surface of each such substrate. The liquid crystal layer does not face the substrates. Reference numeral 20 represents the light guide 20 disposed on the rear surface of the liquid crystal panel 10, which is made of acrylic resin and flecked reflective paint or the like printed on the bottom surface thereof. An optical sheet comprising a diffusion sheet 21 and a prism sheet 22 is arranged between the liquid crystal panel 10 and the light guide 20, and a reflector 23 is arranged on the rear surface of the light guide.
Reference numeral 30 represents the linear light source comprising a cold cathode tube, which is arranged on the side of the light guide 20. Lamp holders 40 for supporting and affixing the linear light source 30 are attached on both ends of the linear light source 30 for the purpose of covering a portion of the glass tube of the linear light source and a portion of the lead wires 35 extending from the electrodes and the end portions of the linear light source. Further, the lamp holders 40 are shaped in such manner as to engage with the corner periphery of a case 50 that houses the light guide 20 and the linear light source 30.
Reference numeral 60 represents a horseshoe-shaped lamp house covering the linear light source along the longitudinal direction of the linear light source 30, such that light emitted from the linear light source 30 efficiently strikes the side surface of the light guide 20.
Reference numeral 70 represents an inner frame for supporting and affixing the liquid crystal panel 10. Then, the lead wires 35 leading out from the lamp holders 40 are laid in spaces formed between the case 50, the lamp house 60, and the inner frame 70. Further, a front frame 80, whose cross-section is approximately L-shaped, is arranged so as to cover the periphery of the front end portion of the liquid crystal panel 10.
Because of its ability to provide backlight to portable products, the sidelight-type backlight is often used. Accordingly, further space saving is desired, and a narrow frame is realized by providing a tapered portion on the lamp holder to shorten the distance between the linear light source and the light guide, as described in JP 11-258601 A1, by way of example.
On the other hand, there is a risk that an unexpected impact will be applied to the portable instrument or apparatus during transport. When the distance between the linear light source and the light guide becomes smaller, as described in JP 11-258601 A1, the linear light source may be damaged due to impact when it contacts the light guide. Even if the linear light source and the light guide do not make contact directly, the impact is nevertheless transmitted to the light guide via the thin lamp holders causing damage to the linear light source.
To prevent the linear light source and the light guide from coming into contact with each other, cubic lamp holders, positioned between the linear light source and the light guide (see Japanese Patent Laid-Open No. 10-96900 publication [JP, 10-096900, A1]), are provided near both ends of the linear light source, while in some cases, nails may be provided. However, since the potential contact area between the side surface of the cubic lamp holders and the light guide is very large, light is blocked in an amount corresponding to the contact area, and a large shadow forms on the light guide. In addition, since large quantities of light are blocked when nails are used as well, a large shadow likewise forms on the light guide. Therefore, when such a configuration is employed, the light traveling in the light guide is largely uneven, which consequently results in light of uneven brightness being emitted toward the liquid crystal panel.